Stroke ranks behind heart disease and cancer as the third cause of death. As a cause of permanent long-term disability it has few equals, and the economic cost to America approximates 6 billion dollars. The technical capability of anastomosing extracranial to intracranial arteries has been developed. It is being postulated as a significant procedure in stroke prevention. As yet, it remains to be established on a firm scientific basis that it is effective in reducing the symptoms of minor stroke or effective in delaying or eliminating the prospect of a major stroke. The procedure is being used with increasing frequency. A randomized trial with collaborating centres agreeing to a strict protocol, and agreeing to place patients who fulfill the criteria of entry into the trail will be conducted in 25-30 collaborative centres with an average follow-up per case of five years. Two major clinical cateogories of patients will be accepted: those with transient ischemic attacks (TIA) and reversible ischemic neurological disability (RIND), and secondly partial non-progressing stroke (stepwise or "slow") and a completed but non-calamitous stroke.